Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	6 Months Ended	9 Months Ended		77 Months Ended
	Jul. 02, 2021	Jun. 29, 2021	Aug. 31, 2019	Jun. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021
Class Of Stock [Line Items]
Proceeds from common stock offering							$ 1,815,700
Follow-on Offering [Member]
Class Of Stock [Line Items]
Proceeds from common stock offering					$ 648,315	$ 107,732	1,086,900
2019 Sales Agreement [Member]
Class Of Stock [Line Items]
Proceeds from common stock offering					$ 45,300	$ 14,700
Percentage of gross proceeds from common stock as sales agent cash commission					3.00%
Stock Issued During Period Shares New Issues				641,709		1,107,100
Common stock price per share				$ 72.79		$ 13.78
Proceeds from common stock offering					$ 47,400		$ 47,400
2019 Sales Agreement [Member] | General and Administrative Expenses [Member]
Class Of Stock [Line Items]
Legal accounting and other fees					$ 100	$ 100
2019 Sales Agreement [Member] | Maximum [Member]
Class Of Stock [Line Items]
Proceeds from common stock offering			$ 150,000
Underwriting Agreement [Member] | Follow-on Offering [Member]
Class Of Stock [Line Items]
Proceeds from common stock offering	$ 648,300
Stock Issued During Period Shares New Issues		4,758,620
Common stock price per share		$ 145.00
Underwriting discounts and estimated offering costs	$ 41,700